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The use of Diagnostic Imaging for Identifying Abnormal Gas Accumulations in Cetaceans and Pinnipeds.

Dennison S, Fahlman A, Moore M - Front Physiol (2012)

Bottom Line: Lung compression and alveolar collapse that terminate gas-exchange before a depth is reached where supersaturation is significant and bradycardia with peripheral vasoconstriction affecting the distribution, and dynamics of blood and tissue nitrogen levels.Published accounts of gas and fat emboli and dysbaric osteonecrosis in marine mammals and theoretical modeling have challenged this view-point, suggesting that decompression-like symptoms may occur under certain circumstances, contrary to common belief.The presence of gas may be asymptomatic and must be interpreted cautiously alongside all other available data including clinical examination, clinical laboratory testing, gas analysis, necropsy examination, and histology results.

View Article: PubMed Central - PubMed

Affiliation: Marine Mammal Radiology San Francisco, CA, USA.

ABSTRACT
Recent dogma suggested that marine mammals are not at risk of decompression sickness due to a number of evolutionary adaptations. Several proposed adaptations exist. Lung compression and alveolar collapse that terminate gas-exchange before a depth is reached where supersaturation is significant and bradycardia with peripheral vasoconstriction affecting the distribution, and dynamics of blood and tissue nitrogen levels. Published accounts of gas and fat emboli and dysbaric osteonecrosis in marine mammals and theoretical modeling have challenged this view-point, suggesting that decompression-like symptoms may occur under certain circumstances, contrary to common belief. Diagnostic imaging modalities are invaluable tools for the non-invasive examination of animals for evidence of gas and have been used to demonstrate the presence of incidental decompression-related renal gas accumulations in some stranded cetaceans. Diagnostic imaging has also contributed to the recognition of clinically significant gas accumulations in live and dead cetaceans and pinnipeds. Understanding the appropriate application and limitations of the available imaging modalities is important for accurate interpretation of results. The presence of gas may be asymptomatic and must be interpreted cautiously alongside all other available data including clinical examination, clinical laboratory testing, gas analysis, necropsy examination, and histology results.

No MeSH data available.


Related in: MedlinePlus

Magnetic resonance imaging images from a California sea lion (Zalophus californianus) to demonstrate the appearance of gas and the associated susceptibility artifact. Both images are at the same level on the same patient. T2W is a regular MRI sequence and T2*W is sensitive to susceptibility artifact. The air within the bulla (*) on the T2W image can be seen and the inner ear structures (arrow) are also present. The same image is shown after T2*W acquisition and the amount of gas within and overall size of the bulla looks larger and the “blooming” effect of the susceptibility artifact due to an air-tissue interface results in loss of conspicuity of the inner ear structures. If abnormal gas were present in the inner ear, it would not be identifiable from this image.
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Figure 4: Magnetic resonance imaging images from a California sea lion (Zalophus californianus) to demonstrate the appearance of gas and the associated susceptibility artifact. Both images are at the same level on the same patient. T2W is a regular MRI sequence and T2*W is sensitive to susceptibility artifact. The air within the bulla (*) on the T2W image can be seen and the inner ear structures (arrow) are also present. The same image is shown after T2*W acquisition and the amount of gas within and overall size of the bulla looks larger and the “blooming” effect of the susceptibility artifact due to an air-tissue interface results in loss of conspicuity of the inner ear structures. If abnormal gas were present in the inner ear, it would not be identifiable from this image.

Mentions: Normal accumulations of gas may obscure adjacent abnormal gas on MRI due to susceptibility artifact ad resolution limitations, Figure 4. Cases have been published, however, where MRI has been successful at identifying intestinal wall gas (pneumatosis intestinalis) in intestines that contain normal luminal gas (Rabushka and Kuhlman, 1994). Cerebellar gas has been successfully diagnosed using MRI in a California sea lion (Van Bonn et al., 2011).


The use of Diagnostic Imaging for Identifying Abnormal Gas Accumulations in Cetaceans and Pinnipeds.

Dennison S, Fahlman A, Moore M - Front Physiol (2012)

Magnetic resonance imaging images from a California sea lion (Zalophus californianus) to demonstrate the appearance of gas and the associated susceptibility artifact. Both images are at the same level on the same patient. T2W is a regular MRI sequence and T2*W is sensitive to susceptibility artifact. The air within the bulla (*) on the T2W image can be seen and the inner ear structures (arrow) are also present. The same image is shown after T2*W acquisition and the amount of gas within and overall size of the bulla looks larger and the “blooming” effect of the susceptibility artifact due to an air-tissue interface results in loss of conspicuity of the inner ear structures. If abnormal gas were present in the inner ear, it would not be identifiable from this image.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3368393&req=5

Figure 4: Magnetic resonance imaging images from a California sea lion (Zalophus californianus) to demonstrate the appearance of gas and the associated susceptibility artifact. Both images are at the same level on the same patient. T2W is a regular MRI sequence and T2*W is sensitive to susceptibility artifact. The air within the bulla (*) on the T2W image can be seen and the inner ear structures (arrow) are also present. The same image is shown after T2*W acquisition and the amount of gas within and overall size of the bulla looks larger and the “blooming” effect of the susceptibility artifact due to an air-tissue interface results in loss of conspicuity of the inner ear structures. If abnormal gas were present in the inner ear, it would not be identifiable from this image.
Mentions: Normal accumulations of gas may obscure adjacent abnormal gas on MRI due to susceptibility artifact ad resolution limitations, Figure 4. Cases have been published, however, where MRI has been successful at identifying intestinal wall gas (pneumatosis intestinalis) in intestines that contain normal luminal gas (Rabushka and Kuhlman, 1994). Cerebellar gas has been successfully diagnosed using MRI in a California sea lion (Van Bonn et al., 2011).

Bottom Line: Lung compression and alveolar collapse that terminate gas-exchange before a depth is reached where supersaturation is significant and bradycardia with peripheral vasoconstriction affecting the distribution, and dynamics of blood and tissue nitrogen levels.Published accounts of gas and fat emboli and dysbaric osteonecrosis in marine mammals and theoretical modeling have challenged this view-point, suggesting that decompression-like symptoms may occur under certain circumstances, contrary to common belief.The presence of gas may be asymptomatic and must be interpreted cautiously alongside all other available data including clinical examination, clinical laboratory testing, gas analysis, necropsy examination, and histology results.

View Article: PubMed Central - PubMed

Affiliation: Marine Mammal Radiology San Francisco, CA, USA.

ABSTRACT
Recent dogma suggested that marine mammals are not at risk of decompression sickness due to a number of evolutionary adaptations. Several proposed adaptations exist. Lung compression and alveolar collapse that terminate gas-exchange before a depth is reached where supersaturation is significant and bradycardia with peripheral vasoconstriction affecting the distribution, and dynamics of blood and tissue nitrogen levels. Published accounts of gas and fat emboli and dysbaric osteonecrosis in marine mammals and theoretical modeling have challenged this view-point, suggesting that decompression-like symptoms may occur under certain circumstances, contrary to common belief. Diagnostic imaging modalities are invaluable tools for the non-invasive examination of animals for evidence of gas and have been used to demonstrate the presence of incidental decompression-related renal gas accumulations in some stranded cetaceans. Diagnostic imaging has also contributed to the recognition of clinically significant gas accumulations in live and dead cetaceans and pinnipeds. Understanding the appropriate application and limitations of the available imaging modalities is important for accurate interpretation of results. The presence of gas may be asymptomatic and must be interpreted cautiously alongside all other available data including clinical examination, clinical laboratory testing, gas analysis, necropsy examination, and histology results.

No MeSH data available.


Related in: MedlinePlus